Resonant four-photon photoemission from SnSe2(001)

IF 6.5 2区 物理与天体物理 Q1 PHYSICS, MULTIDISCIPLINARY
Chengxiang Jiao, Kai Huang, Hongli Guo, Xingxia Cui, Qing Yuan, Cancan Lou, Guangqiang Mei, Chunlong Wu, Nan Xu, Limin Cao, Min Feng
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Abstract

High-order nonlinear multiphoton absorption is usually inefficient, but can be enhanced by designing resonant excitations between occupied and unoccupied energy levels. We conducted angle-resolved multi-photon photoemission (mPPE) studies on the SnSe2(001) surfaces excited by ultrashort laser pulses. By tuning photon energy and light polarization, we demonstrate the presence of a resonant four-photon photoemission (4PPE) process involving the occupied valence band (VB), the unoccupied second conduction band (CB2) and the unoccupied image-potential state (IPs) of SnSe2. In this 4PPE process, VB electrons of SnSe2 are resonantly excited into CB2 by adsorbing two photons, followed by the adsorption of another photon to populate the n = 1 IPs before being emitted out to the vacuum by adsorbing one more photon. This results in a double-resonant 4PPE process, which exhibits approximately a 40 times enhancement in photoemission yields compared to cases where one of the resonant pathways, CB2 → IPs, is inhibited by involving a virtual state instead of the IPs in the 4PPE. The double-resonant 4PPE process efficiently excite the bulk VB electrons outside the vacuum, like taking advantage of resonant “ladders” through two real empty electronic states of SnSe2. Our results highlight the important applications of mPPE in probing the band-structure, particularly the unoccupied states, of recently emerging main group dichalcogenide semiconductors. Furthermore, the discovered resonant mPPE process contributes to the exploration of their promising optoelectronic applications.

Abstract Image

SnSe2(001)的共振四光子光发射
高阶非线性多光子吸收通常效率不高,但可以通过设计占用能级和未占用能级之间的共振激发来增强吸收。我们对超短激光脉冲激发的 SnSe2(001)表面进行了角度分辨多光子光发射(mPPE)研究。通过调整光子能量和光偏振,我们证明了共振四光子光发射(4PPE)过程的存在,该过程涉及 SnSe2 的占用价带(VB)、未占用的第二导带(CB2)和未占用的像势态(IPs)。在这个 4PPE 过程中,SnSe2 的 VB 电子通过吸附两个光子共振激发到 CB2,然后吸附另一个光子填充 n = 1 IPs,最后再吸附一个光子发射到真空中。这就产生了一个双共振 4PPE 过程,与共振途径之一(CB2 → IPs)被抑制的情况相比,该过程的光发射率提高了约 40 倍。双共振 4PPE 过程在真空外有效地激发了块状 VB 电子,就像利用共振 "梯子 "通过 SnSe2 的两个真实空电子态一样。我们的研究结果凸显了 mPPE 在探测最近出现的主族二卤化物半导体带状结构,特别是未占据态方面的重要应用。此外,所发现的共振 mPPE 过程还有助于探索它们的光电应用前景。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Frontiers of Physics
Frontiers of Physics PHYSICS, MULTIDISCIPLINARY-
CiteScore
9.20
自引率
9.30%
发文量
898
审稿时长
6-12 weeks
期刊介绍: Frontiers of Physics is an international peer-reviewed journal dedicated to showcasing the latest advancements and significant progress in various research areas within the field of physics. The journal's scope is broad, covering a range of topics that include: Quantum computation and quantum information Atomic, molecular, and optical physics Condensed matter physics, material sciences, and interdisciplinary research Particle, nuclear physics, astrophysics, and cosmology The journal's mission is to highlight frontier achievements, hot topics, and cross-disciplinary points in physics, facilitating communication and idea exchange among physicists both in China and internationally. It serves as a platform for researchers to share their findings and insights, fostering collaboration and innovation across different areas of physics.
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